A previously healthy 42 year-old woman presented at her family doctor after her hairdresser noticed a nodule in the left temporo-parietal area of the scalp. The mass was a firm, reddish nodule measuring approximately 3 × 2 cm. The patient was completely asymptomatic. She was referred to dermatology, and the lesion was excised. The initial pathology report showed a moderately-well differentiated adenocarcinoma. It was unclear at this time whether this was a primary lesion of the sweat gland or metastatic adenocarcinoma from another site. She was then referred to our centre for oncologic work-up.The pathology was reviewed and confirmed a moderately differentiated adenocarcinoma (Figure 1). The tumour was formed by single tubules or complex back to back tubular structures with areas where the luminal cells showed apical snouts. The lesion filled the reticular dermis without involving the epidermis. No perineural or lymphovascular invasion was present. The resection margins were clear, with the closest margin at 2 mm. The immunohistochemistry showed positivity for CK 7, ER, PR, Androgen receptor, CDX2, Ber ep4 and EMA. It was found to be negative for High molecular weight keratin, CK 20, COX2, CDX2, TTF1, Renal cell marker, CD 117, and CEA. It was concluded that this profile was most consistent with a metastatic breast carcinoma; however an eccrine/apocrine carcinoma of the skin could not be completely ruled out.On physical examination, there was no palpable lymphadenopathy of the neck, supraclavicular or infraclavicular regions bilaterally. No pre-or postauricular lymphadenopathy. On the left temporal parietal scalp, there was a 3 cm, well-healed scar, with no signs of infection or
IntroductionPrimary cutaneous apocrine carcinoma (PCAC) is a rare type of sweat gland neoplasm with incidence rates estimated to range from 0.0049-0.0173 per 100,000 patients per year [1]. Approximately 200 total cases are reported in the literature. PCAC occurs in areas with large numbers of apocrine glands [2]. The scalp is among one of the rarest sites of occurrence, while the axilla appears most commonly [3]. Among the 186 cases reviewed by Hollowell, equal distribution was present in both males and females, with 76% of the sample population of Caucasian ethnicity. Median age was calculated at 67 years for this sample, which is the largest cohort studied to date [1].PCAC can develop in the dermal and subcutaneous layers of the skin, occasionally infiltrating the epidermal layer resulting in ulceration. PCAC has a diverse presentation, occurring as both uniand multi-nodular growths with varying colour [2]. Often these neoplasms are indurated, painless masses and can be associated with benign lesions [2], including a nevus sebaceous, most commonly seen with scalp lesions [4][5][6]. Development of these lesions typically occurs within a year before diagnosis [7]; however several cases have reported longer durations with a period of rapid growth [4,5,8,9]. PCAC is often quite difficult to differentiate from metastases of adenocarcinoma o...