Lymph Node Involvement by a Clear Cell Nodular Hidradenoma-Like Tumor of Uncertain Malignant Potential

A rare case of hidradenocarcinoma with anaplastic and invasive features arising from a nodulocystic hidradenoma

A 91-year-old man presented with a cutaneous left abdominal mass. The mass was longstanding (over 5 years) and slow-growing. Examination revealed a violaceous, multinodular, and exophytic non-tender mass surrounded by patchy erythema. Excisional biopsy was performed and revealed a nodular and cystic dermal proliferation of predominately basaloid cells with focal duct formation, surrounded by prominent hyalinized stroma. The superficial portion of the mass was identified as a nodulocystic hidradenoma. Along the deep aspect and in association with the benign hidradenoma, sheets of markedly atypical epithelioid cells invaded the surrounding tissue, consistent with malignant transformation. Perineural and lymphovascular invasion were seen among areas with anaplastic features. This case supports that some hidradenocarcinoma originates from benign counterparts, and as such, ample sampling is required to definitively exclude a more sinister diagnosis. Diagnostic, prognostic, histopathological, and molecular characteristics, and current knowledge limitations are briefly discussed.

Genetic and Immunohistochemical Profiling of Mammary Hidradenoma and Comparison to Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is exceedingly rare in the breast, with <45 cases reported in the literature. Although estrogen receptor/progesterone receptor/human epidermal growth factor 2 triple-negative, MEC is characterized as a special subtype of breast carcinoma with significantly better prognosis than conventional basal-type tumors. Cutaneous hidradenoma (HA) is considered a benign adnexal neoplasm showing histomorphologic overlap with MEC. Rare cases of HA have also been reported in the breast, but these are relatively uncharacterized. In this study, we examined the clinicopathologic, immunohistochemical (IHC), and genetic features of 8 breast HAs, in comparison to 3 mammary MECs. All cases were positive for MAML2 break-apart fluorescence in situ hybridization. Eight cases demonstrated a CRTC1::MAML2 fusion, and one MEC harbored a CRTC3::MAML2 fusion; the latter is a novel finding in the breast. Mutational burden was very low, with only one HA exhibiting a MAP3K1 pathogenic alteration. By IHC, both MEC and HA demonstrated cell type-dependent expression of high- and low-molecular-weight keratins and p63, as well as negative to low-positive estrogen receptor and androgen receptor. Smooth muscle myosin and calponin highlighted an in situ component in the 3 cases of MEC; expression of these myoepithelial markers was negative in HAs. Additional distinguishing characteristics included the growth pattern and tumor architecture, the presence of glandular/luminal cells in HA, and overall higher IHC expression of SOX10, S100 protein, MUC4, and mammaglobin in MEC. Morphologic findings were also compared to a series of 27 cutaneous nonmammary HAs. Mucinous and glandular/luminal cells were identified in significantly more mammary HAs than nonmammary lesions. The findings provide insight into the pathogenesis of MAML2-rearranged neoplasms of the breast, underscore the overlapping genetic features of MEC and HA, and highlight similarities to their extramammary counterparts.

A Case of Clear Cell Hidradenoma Found During Abdominal Cyst Excision

Clear cell hidradenoma (CCH), a rare yet benign finding, is a tumor that originates from sweat glands. It mainly presents as a slow-growing cystic nodule on the scalp or trunk. We report a case of a 60-year-old man who presented with an abdominal subcutaneous mass. This mass was excised and pathology confirmed the presence of CCH, with cytology negative for malignant cells. Although benign, CCHs cannot be confirmed as such until excision and pathologic analysis, which is the standard treatment of choice.

Three Cases of Clear Cell Hidradenoma With "Benign" Lymph Node Involvement

ABSTRACT

The malignant counterpart of cutaneous clear cell hidradenoma (CCH), hidradenocarcinoma, is an aggressive neoplasm that may have a fatal outcome. However, some cases of benign looking CCH with isolated lymph node involvement and excellent prognosis have been described. "CCH-like neoplasm of uncertain malignant potential" or "atypical hidradenoma" have been proposed as designations for these lesions. We report 3 cases of CCH with lymph node involvement. Ages ranged from 29 to 51 years old. All cases involved the inguinal lymph nodes: 2 of them presented with an isolated lymph node lesion, and the third case had lymph node and cutaneous involvement following the resection of a previous cutaneous lesion. Imaging studies showed no systemic involvement. None of the lesions exhibited histopathologic features of malignancy. All neoplasms were well circumscribed, had cystic spaces, did not display atypia or necrosis, and had less than 4 mitoses per high power field. No recurrence has been observed at follow-up after resection in all cases. All published cases of CCH with lymph node involvement so far affected a single lymph node in the axillary or inguinal regions, lacked features of malignancy, and had excellent long-term prognosis. Some cases previously reported as hidradenocarcinoma probably fit into this category. Our series adds more evidence to this rare phenomenon of "benign metastasis." Aggressive treatment should be avoided in these cases, and a long-term follow-up is warranted.

Cytokeratin expression in epidermal stem cells in skin adnexal tumors

The expression levels of seven types of cytokeratin (CK) in different kinds of skin adnexal tumors were evaluated. One hundred and thirty-two patients with different kinds of skin adnexal tumors admitted and treated in the Department of Dermatology of Dongying People's Hospital from May 2013 to May 2015 were selected and underwent tissue section staining. Another 20 cases of normal skin were enrolled as the control group. The expression levels of the seven types of CK in different kinds of skin appendages were observed and recorded. The expression levels of the seven types of CK in the 132 cases of skin adnexal tumor tissues were different. CK10 was mainly expressed in squamous cell carcinoma, but it was not expressed in basal cell carcinoma. CK19 was expressed in basal cell carcinoma, but its expression was not detected in squamous cell carcinoma. As the degree of differentiation was increased in the epidermis, hair follicle and sebaceous gland, the expressed molecular weight of CK was augmented gradually. The expression levels of five types of CK (namely, CK8, CK10, CK14, CK18 and CK19) could be measured in the squamous cell carcinoma and basal cell carcinoma. Statistical analysis revealed that there were statistically significant differences in the expression levels of these five types of CK in the two cell carcinomas (P<0.05). Five types of CK, i.e., CK7, CK8, CK17, CK18 and CK19, had markedly different expression levels in hair follicle tumor and sweat gland tumor, which were statistically significant (P<0.05). The expression levels of a group of CKs detected by virtue of semi-quantitative analysis via immunohistochemistry can be regarded as one of the important indexes for clinical diagnosis of skin adnexal tumors.