Porocarcinoma

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Adenoid cystic carcinoma of sweat glands

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1. Rosai J. Ackerman's Surgical Pathology. 8th Ed., Mosby-Year Book, St. Louis, 1996; Vol. 1: 125-129.

2. Requena L, Kiryu H, Ackerman AB. Neoplasms with apocrine differentiation. Lippincott-Raven, Philadelphia, 1998, pp. 589-855.

3. Maize JC, Burgdorf WHC, Hurt MA, LeBoit PE, Metcalf JS, Smith T, Solomon AR. Cutaneous Pathology. Churchill Livingstone, Philadelphia, 1998, pp.483-565.

4. Murphy GF, Elder DE. Non-melanocytic tumors of the skin. Atlas of tumors pathology. Fasc. 1, 3rd Series. AFIP, Washington 1991: 90-120.

5. Elder D, Elenitsas R, Ragsdale BD. Tumors of the epidermal appendages. In Elder D, Elenitsas R, Jaworsky C, Johnson B jr. Lever's Histopathology of the skin. 8th Edition. Lippincott-Raven, Philadelphia-New-York, 1997, pp. 747-803.

6. Cooper PH. Carcinomas of sweat glands. Pathol Annu 1987; 22 (p.1): 83-110.

7. Goldstein DJ, Barr RJ, Santa Cruz DJ. Microcystic adnexal carcinoma: a distinct clinicopathologic entity. Cancer 1982; 50: 566-572.

Despite of the great amount of data obtained in the last 20 years, sweat gland carcinomas still now represent a difficult and controversial chapter of pathology. If classifications used in 90's are compared, in fact, it appears that the number of tumors varies according the different authors. In fact, the number of the entities tend to increase: from the 9 tumors reported by Rosai [1] to the 19 considered by Requena et al. in 1998 [2]. Some histological types appear universally accepted, including: porocarcinoma, adenoid cystic carcinoma, mucinous carcinoma, malignant mixed tumor, cylindrocarcinoma, spiradenocarcinoma. All the other tumors pose problems of classification. Hidroadenocarcinoma is not reported by Maize et al., who include it in the category of porocarcinoma [3]. Apocrine carcinoma is not considered by Requena et al., who consider its different morphologic forms as different diagnostic categories [2]. Papillary digital aggressive adenoma/adenocarcinoma is not cited by Rosai [1]; it, however, is reported by Requena et al. as papillary carcinoma [2]. Eccrine adenocarcinoma is an entity recorded by Murphy e Elder [4] and by Elder et al. [5]; it is, however, ignored by all other authors. Elder et al. [5] describe mucoepidermoid carcinoma, considering it as a synonim of adenosquamous carcinoma; Maize et al., however, consider such two entities as different [3]. Only Requena et al. record tubular carcinoma, ductal carcinoma, cribriform carcinoma, papillary hidradenocarcinoma and basal cell carcinoma with apocrine differentiation [2]. They also describe separately microcystic carcinoma, syringomatous carcinoma and solid carcinoma, whereas other describe them as a single entity [6].

Porocarcinoma, the most frequent among sweat gland carcinomas, is composed by squamoid, sometimes clear, cells. It shows a differentiation towards the terminal part of the sweat duct (acrosyringium) and a solid-custic architecture (Figure top). In some cases, it presents itself as a verrucous plaque, sometimes ulcerated, and shows an horizontal growth with prominent intraepidermal component; in other cases it is a nodule, frequently ulcerated, with a prevalent vertical growth. The realationship between this tumor and (clear cell) hidroadenocarcinoma is controversial. At the end of 60's, a unique diagnostic category including both the tumors (malignant acrospiroma) was proposed [6]. In the 90's, however, these two tumors tend to be considered as separate entities [2,4-5]. Such tumors are surely closely related and sometimes are hardly distinguishable, because their architecture is similar, because hidroadenocarcinoma may be composed by eosinophilic, poroid-like,cells, and because porocarcinoma may show clear cells.

Syringomatous carcinoma is a nodular or plaque-like lesion, rarely ulcerated. It is locally invasive and frequently recurs, but it does not metastatize. Histologically, it is composed by solid squamous islands, often with a characteristic "tail", horny microcysts, cellular cords and strands, ductal structures and desmoplastic stroma. This entity poses several problems as well. It was firstly described as microcystic adnexal carcinoma and considered to show a mixed differentiation, toward the sweat duct (ductal structures) and toward the hair follicle (horny microcysts) [7]. Subsequently, however, horny cysts were reinterpreted as an expression of acrosyringial differentiation and the tumor was renamed as sclerosing sweat duct (syringomatous) carcinoma [6]. The problem of the differentiation line remained, however, open. Recently, microcystic adnexal carcinoma and syringomatous carcinoma have been considered as two distinct entities [2]; the reasons of such a pointview, however, do not appear convincing.

Ductal carcinoma is a tumor (or a group of tumors) which shows a differentiation oriented toward the dermal part of the sweat duct and displays a close resemblance to duct carcinoma of the breast. It may show different grades of differentiation: some tumors are composed of uniform and regular ducts (well differentiated tumors), some show ductal, cribriform and solid structures (moderately differentiated tumors), some solid masses and cellular cords, in which a rudimental lumen may be seen (poorly differentiated tumors). Some authors consider such a spectrum of forms as different tumors, describing tubular carcinoma and cribriform carcinoma, explicitly recalling the classification of breast carcinoma [2].

Mucinous carcinoma is a relatively rare tumor composed of smal cellular aggregrates floating in large mucin pools. Such a tumor must be distinguished from mucinous carcinomas from other organs, firsty from breast carcinoma [2,4-6]. Adenoid cystic carcinoma is one of the rarest form of sweat gland carcinoma. In fact, cases reported in the world literature are only about 45 (Figure bottom). Histologically, it shows basaloid cells having a moderate grade of atypia, arranged in tubular, cribriform and solid structures [2,4-6].

Syringocystoadenocarcinoma papilliferum is very rare; very few cases are described in the literature [3].