Malignant eccrine poroma in an unusual location¹

Abstract

Malignant eccrine poroma is a rare skin appendage tumour, originating from the intraepidermal and upper dermal eccrine ducts. The tumour either arises spontaneously or develops in a long-standing eccrine poroma, generally in elderly people over 60. Clinically, it tends to be a localized lesion, which manifests itself as a nodule or ulcerated tumour, favouring extremities. We report an 83-year-old female with an enlarging and bleeding tumour on her lumbosacral region. This lesion first appeared as a small pigmented papule and progressed to an erythematous patch with central papular portion and some peripheral pigmentation. Histopathology revealed malignant eccrine poroma. Also, immunohistochemically, diffuse and intense p53 staining was observed. Regular pigment pattern, brown globules and black dots were seen in dermoscopic examination. After performing a wide excision, 20 months of follow-up revealed no recurrence or metastasis of the tumour. This case represents an unusually located malignant eccrine poroma with some pigmentation.

Altered Rb, p16, and p53 expression is specific for porocarcinoma relative to poroma

“…In our cohort, a high percentage of cells in poromas showed weak p53 staining; evaluation of p53 staining intensity was therefore critical for distinguishing mutation‐associated p53 overexpression in porocarcinoma from diffuse but predominantly weak expression in poromas. In agreement with our findings, strong p53 expression has been reported in porocarcinoma but has been found to be rare or absent in poromas . Also in agreement with our findings, an inverse correlation between p16 and Rb expression has been previously described in porocarcinoma; our results confirm this observation and further link this pattern to truncating RB1 mutations.…”

“…Our study further benefits from correlation with mutation status of the relevant genes in a subset of cases. Some previous reports have not found a significant difference between poromas and porocarcinomas in the percentage of cells labeling for p53 [9][10][11][12][13] ; however, many of these studies did not account for staining intensity. In our cohort, a high percentage of cells in poromas showed weak p53 staining; evaluation of p53 staining intensity was therefore critical for distinguishing mutation-associated p53 overexpression in porocarcinoma from diffuse but predominantly weak expression in poromas.…”

“…Previous studies have examined p53, Rb, or p16 staining in the context of poromas and/or porocarcinomas, although to our knowledge our study is the first to rigorously examine the combined performance of all three markers. Our study further benefits from correlation with mutation status of the relevant genes in a subset of cases.…”

“…Previous immunohistochemical studies on these markers in poromas and porocarcinomas have been limited and yielded contradictory results. 4,[8][9][10][11][12][13][14] Our initial studies indicated that p53 expression may correlate with TP53 mutation status in porocarcinomas, 4 with dominant negative mutations associated with overexpression of p53 protein predicted to lack tumor suppressor activity, and truncating mutations associated with diffuse loss of p53 expression. We investigated whether p53, Rb, and p16 marker expression correlated with mutational status in porocarcinomas, and whether a panel immunohistochemistry approach including these tumor suppressors distinguished porocarcinomas from poromas.…”

A Large Lumbar Adnexal Neoplasm Presenting Characteristics of Eccrine Poroma and Poroid Hidradenoma

“…Still poromas should be excised as they can undergo malignant differentiation [7]. p53 mutations are thought to play an important role in malignant transformation for poroma to poroid carcinoma [8]. …”