Rarely SC occurs in Muir Torre syndrome MTS with at

Rarely, SC occurs in Muir-Torre syndrome (MTS), with at least an associated visceral malignancy (usually a gastrointestinal carcinoma, occurs less in other organs) that may precede or follow the SC. Therefore, SC sometimes is a diagnostic sign of MTS.

Case report
A 56-year-old woman visited a surgical clinician with a firm, mildly eroded, gradually enlarging light yellow nodule measuring about 0.5 cm located eccentrically on her left nipple, which had been noticed a few weeks earlier (Figure 1). She had no other cutaneous tumor, breast tumor, regional lymphadenopathy, or any clinical evidence of other internal malignancy.
Histopathologically, the lesion in the partially excised nipple (cut into 3 sections) showed mainly intraepidermal proliferation in a broad zone of the basal part of the epidermis, with many large and occasionally connecting blunt bulbous downward extensions (only slightly more than 1 mm in depth) composed of atypical/hyperchromatic oval germinative cells, frequently owning clear to fine multivesicular cytoplasm with various degrees of sebaceous differentiation, and occasionally with small foci exhibiting some features of holocrine secretion/abortive sebaceous ducts (Figure 2A, B, C and D). The mature neoplastic sebocytes, differentiating/transitional cells, and immature germinative StemRegenin 1 were haphazardly arranged with a variable ratio; the average ratio was about 1:2:2. The tumor cells possessed atypical round to irregular vesicular nuclei with obvious nucleoli and occasional scalloped nuclear membrane, and exhibited sporadic necrosis and frequent mitoses [counting from 1 to 6 in most high-power fields (HPFs), about 20/10 HPFs on average]. Focally there were some small nests of atypical sebocytes invading the upper dermis (Figure 2C and E) but no prominent haphazard intradermal growth of invasive tumor lobules. No aggregations of uniform basaloid cells with peripheral palisading and retraction artifact from stroma were seen. Few individual and small clusters of tumor cells showed a pagetoid feature in the epidermis, while the epidermis lacked atypical keratinocytes. No lymphatic–capillary permeation was found. Many tumor cells showed immunoreactivity for cytokeratin (CK) 7 (OV-TL 12/30; Dako) and epithelial membrane antigen (EMA) (E29; Dako), with more intensity in those fairly or frankly differentiated tumor cells (Figure 3A); some tumor cells were positive for CD15 (Carb-3; Dako); a minority of tumor cells were positive for humen epithelial antigen (Ber-EP4, Dako) and CK5/6 (D5/16 B4; Dako); and none were positive for carcinoembryonic antigen (CEA) (II-7; Dako) or gross cystic disease fluid protein 15 (GCDFP-15) (23A3; Dako). CK5/6 also more intensely stained the basal–suprabasal layers of epidermis and highlighted the residual normal basal cells in the lower periphery of the intraepidermal tumor growth (Figure 3B). The proliferative fraction as detected by Ki-67 staining (MIB-1; Dako) was greater than 20% in some HPFs. There was a high percentage of tumor cell staining for p53 (DO-7; Dako), about 50% on average (Figure 3C). In addition, many tumor cells were positive for androgen receptor (AR441; Dako). The immunohistochemical (IHC) study was performed with Dako Autostainer Link48 and the provided ready-to-use antibodies; the antibodies for CK7, EMA, Ber-EP4, CK5/6, CEA, Ki-67, and p53 were produced by Dako Denmark A/S (Glostrup, Denmark); the others were produced by Dako North America (Carpinteria, CA, USA). Based on the particular pathological findings, we made a diagnosis of SC that was predominant in intraepidermal proliferation with superficial dermal invasion.
The lesion was completely removed. Our patient did not undergo lymph node dissection. She had no recurrence of tumor or metastasis during the 23 months of follow-up, and she did not show clinical evidence of MTS either. The subsequent available IHC analysis for expression of DNA mismatch repair gene products (proteins) related to MTS revealed expression of MutL protein homolog 1 (MLH-1) (ES05; Dako North America) and MutS protein homolog 2 (MSH-2) [G219-1129; Roche-Ventana, Rocklin, CA, USA; performed with BenchMark XT (Ventana, Tucson, Ariz, USA)], with diffuse strong MLH-1 staining (Figure 3D) and partial reduction in MSH-2 staining.