Malignant Melanocytic Matricoma: A Rare Skin Tumor That Can Clinically Mimic Melanoma.

Malignant melanocytic matricoma (MMM) is an extremely rare skin malignant neoplasm composed of epithelial cells with matrical differentiation and dendritic melanocytes. We found only 11 cases reported in the literature to date according to the databases consulted (PubMed/Medline, Scopus, and Web of Science). Here, we report a case of MMM in an 86-year-old woman. A histological examination showed a dermal tumor with a deep infiltrative pattern, without an epidermal connection. On immunohistochemical staining, tumor cells were positive for cytokeratin AE1/AE3, p63, and beta-catenin (nuclear and cytoplasmic staining) and negative for HMB45, Melan-A, S-100 protein, and androgen receptor. Melanic antibodies highlighted scattered dendritic melanocytes in tumor sheets. The findings did not support the diagnosis of melanoma, poorly differentiated sebaceous carcinoma, and basal cell carcinoma, but supported the diagnosis of MMM.

Histopathologic and Molecular Features of Cutaneous Melanoma in a Moroccan Population.

Background Cutaneous cancer is the most common malignancy type, among which melanomas are considered the most aggressive and lethal. In Morocco, skin melanoma is the 25th most common cancer. To our knowledge, this is the first and largest Moroccan study specifically describing cutaneous melanoma.  Materials and methods We obtained data for 100 patients diagnosed with cutaneous melanoma in the Department of Pathology of Hassan II University Hospital, Morocco. Clinical, histopathological, molecular, and follow-up data were recorded from pathology request forms and the patient's medical records.  Results The mean age of our patients was 65 years old. Histologically, the most prevalent were the nodular (48%) and acro-lentiginous (38%) melanoma subtypes. A total of 66% of the patients had a Breslow thickness of >4 mm. The presence of ulceration was noted in 46% of cases. The average mitoses was 9/1 mm². A total of 44% of patients had metastatic melanoma at the time of diagnosis. The BRAF V600E mutation was found in six cases, and the C-KIT mutation in five cases. The five-year overall survival and metastasis-free survival were 85% and 15%, respectively. There was a significant correlation between Breslow thickness and Clark's level (p<0.001), histologic subtype (p=0.012), and presence of metastasis (p=0.002). There was a significant difference between the head and neck melanomas and those of the feet, particularly in the histological subtype and the presence of ulceration. BRAF V600E mutation was found in six cases of metastatic melanomas of the head and neck, of which three cases were positive for this mutation, as compared with the 23 cases of acral melanomas, which tested negative for the same mutation.  Conclusion The results of our study showed that cutaneous melanomas were characterized by advanced age at diagnosis and late-stage diagnosis with a high Breslow index. The lower limbs were the most affected sites, especially in the plantar region. The acral lentiginous subtype was the most common. The presence of BRAF V600E mutation was associated with a better prognosis.

Primary Cutaneous Malignant Perivascular Epithelioïd Cell Tumor (PEComa): Case Report With Review of the Literature.

Perivascular epithelioïd cell tumor (PEComa) is a mesenchymal neoplasm with epithelioïd or spindled morphology with numerous thin-walled capillaries between tumor cells. They co-express markers of both melanocytic and smooth muscle differentiation. PEComas are rare, presenting in numerous anatomic sites including lung, kidney, liver, genitourinary tract, soft tissue, and skin. Primary cutaneous PEComas are very rare entity, and malignant ones are even more uncommon. Herein, we report the case of a 92-year-old female which was presenting with 7 cm exophytic, ulcerated, hemorrhagic nodular tumor, and rapidly growing for 8 months over the right thigh. On histologic examination, we found a dermal neoplasm formed by an atypical clear cell tumor with numerous branching capillaries between tumor cells. The mitotic count was found 6 mitotic figures/10 HPF. On immunohistochemistry, tumor cells co-expressed smooth muscle and melanocytic markers, CD10, and CD68. Based on these findings, the diagnosis of primary cutaneous malignant perivascular epithelioïd cell tumor (PEComa) was made. The large size (7 cm), the count of mitoses (6 mitotic figures/10 HPF), and the nuclear pleomorphism argued for malignancy. The absence of soft tissue or visceral localization argued for the cutaneous primitive origin. Adjuvant radiotherapy and targeted therapy with mTOR inhibitor (nab-sirolimus) was indicated. To the best of our knowledge, this is only the eighth case of a primary cutaneous malignant PEComa reported in the literature to date.