Porocarcinoma | |
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Other names | malignant poroma, eccrine porocarcinoma, malignant eccrine poroma |
Specialty | Dermatology, surgery, oncology |
Symptoms | Superficial tumor of an eccrine sweat gland virtually anywhere on the skin |
Complications | Invasion of nearby tissues, recurrence after surgical removal, metastases |
Causes | Unknown |
Prognosis | Metastatic porcarcinomas often have a poor prognosis |
Porocarcinoma (PCA) (also termed malignant poroma, eccrine porocarcinoma, and malignant eccrine poroma) [1] is a rare form of skin cancer that develops in eccrine sweat glands, i.e. the body's widely distributed major type of sweat glands, as opposed to the apocrine sweat glands which are located primarily in the armpits and perineal area. [2] This cancer typically develops in individuals as a single cutaneous tumor in the intraepidermal spiral part (termed the acrosyringium) of these sweat glands' ducts (i.e. channels) at or near to where they open on the skin's surface. [3] PCA tumors are classified as one form of the cutaneous adnexal tumors; [4] in a study of 2,205 cases, PCA was the most common (11.8%) form of these tumors. [5]
Porocarcinomas are malignant counterparts to the far more common benign tumors of the eccrine sweat gland's acrosyringium, i.e. poromas. As currently viewed, there are 4 poroma variants based on their predominant cell types and extent of their tumor tissues presence in the epidermis and dermis: 1) Hidroacanthoma simplexe poromas are confined to the epidermis, i.e. uppermost layer of the skin. 2) Dermal duct poromas are confined to the dermis, i.e. layer of skin between the epidermis and subcutaneous tissues. [1] 3) Hidradenomas have recently been sub-classified into two groups; 95% are termed clear cell hidradenomas and have features suggesting that they derive from apocrine sweat glands while the remaining 5% are termed poroid hidradenomas and have features suggesting that they derive from eccrine sweat glands. [6] And 4) eccrine poromas are eccrine sweat gland tumors that consist of three cell types (see the histopathology section of Poromas) and are primarily located in the epidermis and superficial dermis. Poromas may have 2 or more of these variants in the same tumor tissue and the variants typically have histopathology findings that are not clearly distinguishable from each other. [7] [8] PCA tumors may arise from one of these longstanding poromas [8] (in one study this occurred in 18% of cases [9] ) but more commonly appear to develop independently of any precursor poroma. [1]
PCA are locally invasive tumors [1] that have been treated by surgical resection but often recur at the site of their surgical removal and metastasize to distant tissues before or after their removal. [1] Repeatedly recurrent, unresectable, and metastatic PCA have been treated with chemotherapy and/or radiotherapy. [10] [11] However, metastatic PCA has responded poorly to these treatments and carries a poor prognosis. [12]
Because of their rarity and lack of distinct clinical features and variable physical and microscopic histological appearances, the diagnosis of porocarcinomas is often challenging. [1] PCA has commonly been either mis-diagnosed or over-diagnosed. [4] [9] Under-diagnosis may have been responsible for a recent study conducted in a United Kingdom single center that reported that the number of PCA cases had increased 3-fold over the previous 4 years and was expected to rapidly rise further during the next decade. [9]
In a large study reviewing all literature reports of PCA up to December 1, 2016, patients (including those with a poroma that later progressed to a PCA) presented with a single epidermal nodule or mass (71.2% of cases), ulcerated mass/nodule (18.3%), plaque (9.8%), swelling (1.3%), wart (0.6%), papule (0.6&) or nevus (i.e. mole, 0.6%). The patients were aged 6 months to 97 years old (average age 67.57 years). The lesions presented in the head & neck (39.9% of cases), legs (33.9%), arms (8.8%), back (5.1%), chest wall (4.6%), genitalia (4.0%), abdomen (2.6%), or around the anal area (0.6%) and had been present for as little as 4 days or as long as 60 years (average 5.6 years). Metastasis (most commonly involving the lymph nodes close to the primary lesion) were diagnosed at presentation in 31% of cases. [2] Other studies report that: a) PCA tumors presented with average sizes of 2.53 cm (range of 0.3–7 cm) in largest diameter; [11] b) PCA tumors at presentation were commonly red to violet in color, usually <2 cm in maximum diameter; and typically asymptomatic but may have been called to attention because of spontaneous bleeding, ulceration, sudden itching, pain, or rapid growth; [13] c) in 37 cases, metastases were present in 16.2% of cases at presentation and occurred in two cases (5.4% of cases) 3 and 17 months after diagnosis; [4] d) no metastatic disease was found at presentation or after a 3-year follow-up in 7 cases; [10] e) PCA have metastasized to nearby or distal skin sites, local lymph nodes, or to the bones, bladder, breast, retroperitoneum, ovary, liver, lung, [11] brain, or stomach; [2] and f) PCA have been reported to occur in skin areas previously traumatized or exposed to radiation, excessive sunlight, or chronic lymphedema; in a sebaceous cyst; and in individuals with extramammary Paget's disease, sarcoidosis, chronic lymphocytic leukemia, pernicious anemia, Hodgkin's disease, nevus sebaceous, HIV/AIDS, xeroderma pigmentosum, immunosuppression caused by a disease or chemotherapy, pernicious anemia, and xeroderma pigmentosa. [11] [13]
The microscopic histopathology of benign poroma tumors stained with hematoxylin and eosin dyes consists of poroid cells (i.e. small, round cells with oval nuclei and little cytoplasm) admixed with cuticular cells (i.e. epithelium-like cells) with centrally placed nuclei and abundant eosinophilic (i.e. colored pink or red due to uptake of the eosin stain) cytoplasm. [14] Porocarcinomas differ from poromas by their content of cells that are more irregular in size and contain misshaped nuclei [14] that often have conspicuous nucleoli. [15] Unlike the tumor cells in poromas, PCA tumor cells often appear to invade nearby normal tissues. [1] are rapidly proliferating as evidenced by their increased mitotic activity, and may have differentiated (this process is termed metaplasia) to appear as squamous cells, clear cells, mucous cells, or spindle cells. [11] PCA tissues may contain areas of necrosis (i.e. dead cells). [16]
A large review study reported that PCA tumor cells are periodic acid–Schiff stain positive (30 of 30 tested cases) and express (as detected by immunoassays) epithelial membrane antigen (51 of 51 cases), cytokeratins 1 thru 8, 10, 14 thru 16, and/or 19 as detected using the AE1/AE3 antibody cocktail which detects these but not cytokeratins 17 or 18 (22 of 22 cases), Ki-67 (6 of 6 cases), cytokeratin 7 (15 of 19 cases), TP63 (7 of 7 cases), carcinoembryonic antigen (58 of 61 cases), p53 (7 of 8 cases), and S100 (8 of 21 cases). CK20, synaptophysin, and TTF-1 were not detected in the 10, 4, and 4 cases, respectively, that were tested for these proteins. [17] Another review study reported that PCA tumor cells express cytokeratin 19 (13 of 14 cases), the c-Kit proto-oncogene (11 of 14 cases), and epithelial cell adhesion molecule as detected by BerEp4 staining (8 of 14 cases). [18] A study on one to a few patients reported that these tumor cells express cytokeratin 5, cytokeratin 6, keratin 7, keratin 20, Ki-67, MUC1 and Bcl-2 but not carcinoembryonic antigen, TP63, S100, CD43, or GCDFP15. [19] Finally, a recent study on one patient reported that PCA tumor cells express epithelial membrane antigen, TP63, AE1/AE3 antibody-detected cytokeratins, carcinoembryonic antigen, and microphthalmia-associated transcription factor but not S100, cytokeratin 7, or cytokeratin 20. [20] The presence or absence of these marker proteins is used to support the diagnosis that a skin lesion is a PCA tumor. [18] [19] [20]
A study of 11 porocarcinomas detected a YAP-NUTM1 fusion gene in the tumor cells in 6 cases while a sampling of 104 promos found this fusion gene in 21 cases; the YAP-NUTM1 fusion gene was not detected in a wide range of other skin tumor types. [1] Other studies have found indirect evidence that this fusion gene was expressed in the PCA tissue cells of 5 of 12 [21] and 8 of 40 PCA cases. [22] A fusion gene is an abnormal gene consisting of parts from two different genes that are merged as a result of a large scale gene mutation such as a chromosomal translocation, interstitial deletion, or inversion. The YAP1-NUTM1 fusion gene is a translocation that merges part of the protein coding region of the NUTM1 gene located in band 14 on the long (or "q") arm of chromosome 15 with a part of the YAP1 gene located in band 22.1 on the long (i.e. "q") arm of chromosome 11 [23] Studies on cultured immortalized human dermal keratinocyte (i.e. HDK) cells and mouse embryonic fibroblast NIH-3T3 cells found that YAP1-NUTM1 fusion genes stimulated the anchorage-independent growth of NIH-3T3 cells and activated a transcriptional enhancer factor family member (i.e. TEAD family member) reporter gene. [1] TEAD family transcription factors (also known as transcriptional enhancer factors (TEFs) in humans include four members, TEAD1, TEAD2, TEAD3, and TEAD4 that are transcription factors, i.e. proteins that regulate the expression of various genes. TEAD transcription factors interact with transcription coregulators, including in particular the YAK1 protein, to activate various cell signaling pathways including the Hippo pathway and to regulate cellular maturation, cellular proliferation, and the development of various tissues, organs, and cancers. Cancers associated with the overexpression or overactivation of the TEAD transcription factors include those of the breasts, kidneys, stomach, liver, colon, rectum, prostate, brain (i.e. medulloblastomas), and the head and neck area (i.e. squamous cell carcinomas). [24] [25] [26] It is suggested that the YAP1-NUTM1 fusion gene and the Hippo pathway which it activates may contribute to the development and progression of PCA and serve as therapeutic targets to treat YAP1-NUTM1 fusion gene bearing-PCA tumors. [2] [21] However, further studies are needed to confirm these suggestions. [1] [25] [26] [27] The tumor tissues of CPA have also been reported to express the YAP1-MAML2 fusion gene (1 of 11 cases), [1] the EMC7-NUTM1 (EMC7 is the ER membrane protein complex subunit 7 gene, see endoplasmic reticulum membrane protein complex) fusion gene in a single case, and, in individual cases, mutations in the TP53, RB1, CDKN2A [28] [12] and HRAS [14] tumor suppressor genes. Further studies are needed to determine if the latter fusion or mutated genes can be used as diagnostic markers or therapeutic targets for treating PCA tumors. [1] [28]
The diagnosis of PCA is based on determining that a skin lesion has one of various shapes, presentations, and microscopic histological appearances. However, its diagnosis is considered difficult. [1] PCAs have been misdiagnosed as various disorders including poromas, squamous cell carcinomas, basal cell carcinomas, seborrheic keratosis, nevi (i.e. moles), amelanotic melanomas, [10] superficial spreading melanomas, [12] pyogenic granulomas, fibromas, metastatic adenocarcinomas, verruca vulgaris (i.e. warts), [4] Paget's disease of the breast-associated skin lesions, [12] Merkel cell carcinoma, clear cell hidradenocarcinomas, and skin metastases from other cancers. [16] PCA lesions have histological features which help distinguish them from these other skin lesions: they typically consist of medium-sized, rapidly proliferating cells with atypical nuclei, cell junctions, and intracellular formations of duct-like structures; may have areas of tissue that are necrotic and/or contain partially formed ducts lined with cuboidal/columnar epithelial cells (this last factor is a strong indicator of PCA); [4] and often evidence invasion of nearby tissues. [4] In unclear cases, the expression of key marker proteins by tumor tissue cells, as detected by immunohistochemistry analyses, has been used to clarify the diagnosis. [1] [17] [11] For example, lesions containing tumor cells that express cytokeratins and CK 34B12 but not prostate specific antigen or prostatic specific acid phosphatase; [11] p16 but not retinoblastoma protein; [11] or carcinoembryonic antigen and NUC1 but negative for periodic acid–Schiff staining [4] have been used to support the diagnosis of PCA. Detection of the YAP1-NUTM1 fusion gene transcripts or product protein in the tumor tissue cells of a lesion may also help identify a tumor as either a PCA or poroma. [1] Finally, the presence of metastatic disease would indicate the lesion is not a benign lesion such as a poroma, seborrheic keratosis, nevus, fibroma, or wart. [4] [14]
Prompt management is essential in the treatment of PCA in order to reduce the possibility of developing metastatic disease. [12] Due to its rarity, the best treatment(s) for PCA have not been formally studied and remain unclear. [1] Tumor excision using wide local excision margins or Mohs micrographic surgery to ensure that all malignant tissue is removed have been the most often recommended treatments for localized PCA. [10] Removal of all tumor cells is necessary for curative therapy. [20] Metastases are more likely to be present with PCA lesions that: a) develop spontaneous bleeding, ulceration, sudden itching, pain, or rapid growth; [4] [13] b) are accompanied by enlarged sentinel lymph nodes, i.e. lymph nodes draining the tumor site; [10] c) consist of poorly differentiated cells as detected on biopsy; [11] d) penetrate 7 mm or more into the skin; e) contain rapidly proliferating cells as defined by the presence of 14 or more cells undergoing mitoses per high power microscopic field; [9] or f) occur in the perineum, trunk, or lower limb. [17] In these cases, studies recommend that patients be more fully examined for metastases before surgery using lymphadenectomy (i.e. lymph node dissection) in order to check for metastasis in, and remove, lymph nodes draining the site of the skin tumor [10] and by magnetic resonance, positron emission tomography–computed tomography, X-ray, [17] ultrasound imaging methods [10] to detect metastases. PCA cases in which surgical resection of the primary tumor does not remove all malignant cells or the tumor recurs at its site of removal (~20% recur at the primary site within a year of excision [12] ) have been treated with repeated resections and/or local radiation therapy. Adjuvant radiation therapy may also be useful to treat localized APC tumors that are at high-risk of metastasizing such as tumors that are >5 cm in maximal diameter, have invaded lymphatic vessels, or contain poorly differentiated cells. [16]
Patients that failed to have their disease completely removed with surgical/radiation/lymphadenectomy procedures or have surgically inaccessible metastases are usually treated with various drug regimens. [2] [10] These regimens have included 5-fluorouracil (i.e. 5-FU) alone, 5-FU & cisplatin, 5-FU & Adriamycin & paclitaxel, [4] docetaxel & carboplatin, [11] paclitaxel & carboplatin & intralesional (i.e. injected directly into the lesion) interleukin 2, topical diphenylcyclopropenone (a drug which is primarily used to treat warts), [17] intralesional interleukin 2 alone, interferon alfa & isotretinoin, topical 5-FU, intra-arterial (i.e. injection of a drug into a small artery that supplies blood to a tumor) docetaxel, [29] or the immunotherapy drug, pembrolizumab. [16] [20] The two patients treated with pembrolizumab obtained a complete and excellent responses that continued at follow-up examinations done respectively 24 and 18 months after treatment. [16] [20] In general, however, there has been no highly and repeatedly successful drug treatments specified for metastatic PCA: [11] the cited drug treatment regimens have been used in too few cases to be properly evaluated and in general produced no, minimal, or only very short-term benefits. [2] [10] [11]
Although most studies have observed patients for short periods and do not mention survival times, survival rates, or definitive prognoses, some studies have reported that localize PCA may be successfully treated by surgical removal. However, PCA has often been reported to be a very aggressive malignancy [2] that is a) that is found to be metastatic at diagnosis in approximately 20% to 30% of patients; b) recurs after surgical removal in another ~20% of cases; and c) carries a poor prognosis [10] with survival times that are often just a few months after diagnosis regardless of management. [2] [12] However, a recent study of eight PCA cases found no nodal positivity, recurrence, or death after follow-ups. Further studies are need to define the prognosis of PCA. [30]
Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, are metastases (mets). It is generally distinguished from cancer invasion, which is the direct extension and penetration by cancer cells into neighboring tissues.
A Krukenberg tumor refers to a malignancy in the ovary that metastasized from a primary site, classically the gastrointestinal tract, although it can arise in other tissues such as the breast. Gastric adenocarcinoma, especially at the pylorus, is the most common source. Krukenberg tumors are often found in both ovaries, consistent with its metastatic nature.
Hybridoma technology is a method for producing large numbers of identical antibodies. This process starts by injecting a mouse with an antigen that provokes an immune response. A type of white blood cell, the B cell, produces antibodies that bind to the injected antigen. These antibody producing B-cells are then harvested from the mouse and, in turn, fused with immortal myeloma cancer cells, to produce a hybrid cell line called a hybridoma, which has both the antibody-producing ability of the B-cell and the longevity and reproductivity of the myeloma. The hybridomas can be grown in culture, each culture starting with one viable hybridoma cell, producing cultures each of which consists of genetically identical hybridomas which produce one antibody per culture (monoclonal) rather than mixtures of different antibodies (polyclonal). The myeloma cell line that is used in this process is selected for its ability to grow in tissue culture and for an absence of antibody synthesis. In contrast to polyclonal antibodies, which are mixtures of many different antibody molecules, the monoclonal antibodies produced by each hybridoma line are all chemically identical.
Undifferentiated pleomorphic sarcoma (UPS), also termed pleomorphic myofibrosarcoma, high-grade myofibroblastic sarcoma, and high-grade myofibrosarcoma, is characterized by the World Health Organization (WHO), 2020, as a rare, poorly differentiated neoplasm, i.e. an abnormal growth of cells that have an unclear identity and/or cell of origin. WHO classified it as one of the undifferentiated/unclassified sarcomas in the category of tumors of uncertain differentiation. Sarcomas are cancers known or thought to derive from mesenchymal stem cells that typically develop in bone, muscle, fat, blood vessels, lymphatic vessels, tendons, and ligaments. More than 70 sarcoma subtypes have been described. The UPS subtype of these sarcomas consists of tumor cells that are poorly differentiated and may appear as spindle-shaped cells, histiocytes, and giant cells. UPS is considered a diagnosis that defies formal sub-classification after thorough histologic, immunohistochemical, and ultrastructural examinations fail to identify the type of cells involved.
A papillary hidradenoma, also termed hidradenoma papilliferum or mammary-like gland adenoma of the vulva, is a rare, but nonetheless most common benign tumor that occurs in and between anal and genital regions of females. These hidradenomas are sharply circumscribed, nodular tumors that usually develop in women's anogenital area but uncommonly occur in other sites in women and men. Papillary hidradenomas that develop outside of the anogenital region are termed ecctopic papillary hidradenomas or ectopic hidradenoma papilliferums.
Congenital mesoblastic nephroma, while rare, is the most common kidney neoplasm diagnosed in the first three months of life and accounts for 3-5% of all childhood renal neoplasms. This neoplasm is generally non-aggressive and amenable to surgical removal. However, a readily identifiable subset of these kidney tumors has a more malignant potential and is capable of causing life-threatening metastases. Congenital mesoblastic nephroma was first named as such in 1967 but was recognized decades before this as fetal renal hamartoma or leiomyomatous renal hamartoma.
Malignant acrospiroma, also known as nodular hidradenocarcinoma, malignant nodular clear-cell hidradenoma, mucoepidermoid hidradenocarcinoma, clear-cell hidradenocarcinoma, malignant clear-cell acrospiroma, and clear-cell eccrine carcinoma, is a rare and aggressive tumour of the eccrine sweat glands. It was first documented by Keasbey and Hadley in 1954.
Sebaceous carcinoma, also known as sebaceous gland carcinoma (SGc), sebaceous cell carcinoma, and meibomian gland carcinoma is an uncommon malignant cutaneous tumor. Most are typically about 1.4 cm at presentation. SGc originates from sebaceous glands in the skin and, therefore, may originate anywhere in the body where these glands are found. SGc can be divided into 2 types: periocular and extraocular. The periocular region is rich in sebaceous glands making it a common site of origin. The cause of these lesions in the vast majority of cases is unknown. Occasional cases may be associated with Muir-Torre syndrome. SGc accounts for approximately 0.7% of all skin cancers, and the incidence of SGc is highest in Caucasian, Asian, and Indian populations. Due to the rarity of this tumor and variability in clinical and histological presentation, SGc is often misdiagnosed as an inflammatory condition or a more common neoplasm. SGc is commonly treated with wide local excision or Mohs micrographic surgery, and the relative survival rates at 5 and 10 years are 92.72 and 86.98%, respectively.
Poromas are rare, benign, cutaneous adnexal tumors. Cutaneous adnexal tumors are a group of skin tumors consisting of tissues that have differentiated towards one or more of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. Poromas are eccrine or apocrine sweat gland tumors derived from the cells in the terminal portion of these glands' ducts. This part of the sweat gland duct is termed the acrosyringium and had led to grouping poromas in the acrospiroma class of skin tumors. Here, poromas are regarded as distinct sweat gland tumors that differ from other sweat gland tumors by their characteristic clinical presentations, microscopic histopathology, and the genetic mutations that their neoplastic cells have recently been found to carry.
Spiradenomas (SA) are rare, benign cutaneous adnexal tumors that may progress to become their malignant counterparts, i.e. spiradenocarcinomas (SAC). Cutaneous adnexal tumors are a group of skin tumors consisting of tissues that have differentiated towards one of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. SA and SAC tumors were regarded as eccrine gland tumors and termed eccrine spiradenomas and eccrine spiradenocarcinomas, respectively. However, more recent studies have found them to be hair follicle tumors and commonly term them spiradenomas and spiradenocarcinomas, respectively. Further confusing the situation, SA-like and SAC-like tumors are also 1) manifestations of the inherited disorder, CYLD cutaneous syndrome (CCS), and 2) have repeatedly been confused with an entirely different tumor, adenoid cystic carcinomas of the salivary gland. Here, SA and SAC are strictly defined as sporadic hair follicle tumors that do not include the hereditary CCS spiradenomas and heridtary spiradenocarcinoms of CCS or the adenoid cystic carcinomas.
Eccrine carcinoma is a rare skin condition characterized by a plaque or nodule on the scalp, trunk, or extremities. It originates from the eccrine sweat glands of the skin, accounting for less than 0.01% of diagnosed cutaneous malignancies. Eccrine carcinoma tumors are locally aggressive, with a high rate of recurrence. Lack of reliable immunohistochemical markers and similarity to other common tumors has made identification of eccrine carcinoma difficult.
Malignant pilomatricoma is a cutaneous condition characterized by a locally aggressive tumor composed of hair-matrix cells.
Acrospiromas are a broad class of benign cutaneous adnexal tumors. Cutaneous adnexal tumors are a group of skin tumors consisting of tissues that have differentiated towards one or more of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. Acrospiromas are thought to derive from apocrine or eccrine sweat gland ducts near their acrosyringium, i.e. point where these ducts open to the skin's surface.
Low-grade fibromyxoid sarcoma (LGFMS) is a rare type of low-grade sarcoma first described by H. L. Evans in 1987. LGFMS are soft tissue tumors of the mesenchyme-derived connective tissues; on microscopic examination, they are found to be composed of spindle-shaped cells that resemble fibroblasts. These fibroblastic, spindle-shaped cells are neoplastic cells that in most cases of LGFMS express fusion genes, i.e. genes composed of parts of two different genes that form as a result of mutations. The World Health Organization (2020) classified LGFMS as a specific type of tumor in the category of malignant fibroblastic and myofibroblastic tumors.
Sclerosing epithelioid fibrosarcoma (SEF) is a very rare malignant tumor of soft tissues that on microscopic examination consists of small round or ovoid neoplastic epithelioid fibroblast-like cells, i.e. cells that have features resembling both epithelioid cells and fibroblasts. In 2020, the World Health Organization classified SEF as a distinct tumor type in the category of malignant fibroblastic and myofibroblastic tumors. However, current studies have reported that low-grade fibromyxoid sarcoma (LGFMS) has many clinically and pathologically important features characteristic of SEF; these studies suggest that LGSFMS may be an early form of, and over time progress to become, a SEF. Since the World Health Organization has classified LGFMS as one of the malignant fibroblastic and myofibroblastic tumors that is distinctly different than SEF, SEF and LGFMS are here regarded as different tumor forms.
Mammary secretory carcinoma (MSC), also termed secretory carcinoma of the breast, is a rare form of the breast cancers. MSC usually affects women but in a significant percentage of cases also occurs in men and children. Indeed, McDvitt and Stewart first described MSC in 1966 and termed it juvenile breast carcinoma because an increased number of cases were at that time diagnosed in juvenile females. MSC is the most common form of breast cancer in children, representing 80% of childhood breast cancers, although it accounts for less than 0.15% of all breast cancers.
The nuclear protein in testis gene encodes a 1,132-amino acid protein termed NUT that is expressed almost exclusively in the testes, ovaries, and ciliary ganglion. NUT protein facilitates the acetylation of chromatin by histone acetyltransferase EP300 in testicular spermatids. This acetylation is a form of chromatin remodeling which compacts spermatid chromatin, a critical step required for the normal conduct of spermatogenesis, i.e. the maturation of spermatids into sperm. Male mice that lacked the mouse Nutm1 gene using a gene knockout method had abnormally small testes, lacked sperm in their cauda epididymis, and were completely sterile. These findings indicate that Nutm1 gene is essential for the development of normal fertility in male mice and suggest that the NUTM1 gene may play a similar role in men.
CYLD cutaneous syndrome (CCS) encompasses three rare inherited cutaneous adnexal tumor syndromes: multiple familial trichoepithelioma (MFT1), Brooke–Spiegler syndrome (BSS), and familial cylindromatosis (FC). Cutaneous adnexal tumors are a large group of skin tumors that consist of tissues that have differentiated towards one of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. CCS tumors are hair follicle tumors.
Papillary carcinomas of the breast (PCB), also termed malignant papillary carcinomas of the breast, are rare forms of the breast cancers. The World Health Organization (2019) classified papillary neoplasms of the breast into 5 types: intraductal papilloma, papillary ductal carcinoma in situ (PDCIS), encapsulated papillary carcinoma (EPC), solid-papillary carcinoma (SPC), and invasive papillary carcinoma (IPC). The latter four carcinomas are considered here; intraductal papilloma is a benign neoplasm. The World Health Organization regarded solid papillary carcinoma as having two subtypes: in situ and invasive SPC.
Pure apocrine carcinoma of the breast (PACB) is a rare carcinoma derived from the epithelial cells in the lactiferous ducts of the mammary gland. The mammary gland is an apocrine gland. Its lactiferous ducts have two layers of epithelial cells, a luminal layer which faces the duct's lumen and a basal layer which lies beneath the luminal layer. There are at least four subtypes of epithelial cells in these ducts: luminal progenitor cells and luminal mature cells which reside in the luminal layer and mammary stem cells and basal cells which reside in the basal layer. Examination of the genes expressed in PACB cancer cells indicate that most of these tumors consist of cells derived from luminal cells but a minority of these tumors consist of cells derived from basal cells.