Non-melanocytic Skin Tumors
Moderator: Dr. Philip E. LeBoit
Case 2-3 -
Sebaceous Gland Neoplasm - Adenoma or Carcinoma?
Mark A. Hurt, MD
WCP Pathology PC
Maryland Heights (St. Louis) MO
The patient was an 81 year old man with a mass in the right axillary region. It was thought
clinically to be inflammation. The lesion was diagnosed originally as sebaceous carcinoma, indeterminate
margins, by the original pathologist. I received the biopsy as a second opinion consultation.
Case 2-3 - Slide 1
This sebaceous gland neoplasm consisted of lobules of sebaceous glands that vaguely resembled the
native sebaceous gland, but with many more basophilic cells at the periphery, forming pyramidal
structures that matured to obvious sebocytes with the usual complement of bubbly cytoplasm.
In contrast with sebaceoma (sebaceous adenoma), this patient's neoplasm consisted of discrete lobules
that radiated from central cyst-like structures, and the sebocytes were found easily within it. Despite
the fact that the sebocytes, especially the immature ones, were relatively monomorphous, there were many
mitotic figures in this lesion, some of them abnormal. There was also considerable nuclear crowding,
especially in the less differentiated zones.
Diagnosis: Sebaceous Adenocarcinoma
Historically sebaceous neoplasms were divided into sebaceous adenomas and sebaceous carcinomas (ie,
sebaceous adenocarcinomas). In the 1940's, the term "sebaceous epithelioma" was introduced and is
probably still used by some authors and some diagnosticians. Other names such as "sebomatricoma" have
been used, and, of course, the term "sebaceoma" was introduced in 1984 and Troy and Ackerman.
Early examples of sebaceous neoplasms, such as the one described by Bock in 1880 in Archiv Für
Pathologische Anatomie und Physiologie und Für Klinische Medicin, vol 81, produced a example of a
sebaceous gland neoplasm very similar to the one described in the patient in this seminar. In 1909 Karl
Reitmann, writing in the Arch Derm Syph ( Berlin) 1909; 99:125 presented another lesion very similar to
the one presented herein, again thought to be an adenoma. Another example of a lesion, this time by
American authors, Woolhandler and Becker, writing in the Archives of Dermatology and Syphilology
1942;45:734-56, illustrated, in their case #5, what they considered to be a adenoma of sebaceous glands,
again very similar to the patient presented herein. In that patient, the authors considered the
possibility that the lesion was actually carcinoma. Just one year later, Warren and Warvi, writing in
the Am J Pathol (1943; 19:441), illustrated a lesion they interpreted as adenoma; today most would
identify it readily as sebaceous hyperplasia. They also identified a lesion they termed carcinoma with
invasion of a muscle fiber, it consisting of completely mature sebaceous lobules.
It was Walter F. Lever, MD, writing in the Arch Derm Syph (Chicago) 1948;57:102, who presented a
lesion consisting of very tightly nested basophilic cells, some of which had clear-cut sebaceous
differentiation, but with relatively monomorphous small basophilic cells. One could compare Lever's
cases to those of Troy and Ackerman in 1984, and I believe they are very close to each other. Writing
that same year, in an article on the "pathogenesis of benign tumors of cutaneous appendages of basal cell
epithelioma", Lever described a lesion he termed "sebaceous epithelioma". In that article he argued that
sebaceous epithelioma stood "between sebaceous adenoma with its more typical lobules, on the one hand,
and cystic basal cell epithelioma in which there is only a little differentiation toward sebaceous cells,
on the other" (Arch Derm Syph (Chicago) 1948; 57:679). However, when one looks at Lever's figure 7 from
that paper, it is clear, in retrospect, that the lesion is not an adenoma; it is carcinoma.
Zackheim, writing in the Archives of Dermatology in 1964 (89:711), in an article about sebaceous
epithelioma, regarded these lesions as epitheliomas if "at least half of the cell mass consists of
undifferentiated cells". Yet, in some of the cases that Zackheim presented, it is clear that some of
these lesions are carcinomas with very infiltrative strands of basophilic cells in a dense stroma.
A decade later, Rulon and Helwig, writing in the Am J Clin Pathol (1973;60:745), regarding patients
with the Muir-Torre Syndrome, showed sebaceous gland proliferations very similar to those described by
Zackheim in 1964, the difference being that Zackheim termed those lesions "sebaceous epitheliomas" while
Rulon and Helwig considered them to be "adenomas". One year later, in 1974, Rulon and Helwig again wrote
of "cutaneous sebaceous neoplasms" in Cancer (1974; 33:82), in which they divided sebaceous gland
neoplasms into adenomas, basal cell carcinomas with sebaceous differentiation, and sebaceous carcinomas.
Their concept of sebaceous adenoma consisted of lobular lesions of glands that had relatively mature
sebocytes within them and maintained a lobular, pyramidal structure, similar in many respects, to the
neoplasm presented herein. Some of the lesions they described were cystic and some were mostly solid.
In today's terms, the cystic lesions vs. the relatively solid ones are very different in pattern and the
mostly solid basophilic ones are very similar to those described by Troy and Ackerman in 1984, under the
term "sebaceoma". The concept of sebaceous adenocarcinoma, according to Rulon and Helwig was a
malignancy of pleomorphic sebocytes, one that would often have perineural or intraneural involvement and
would be unmistakable as a malignant neoplasm by virtually any pathologist.
In 1984, the now classic article by Troy and Ackerman was published in the Am J Dermatopathol
(6:7-13). The lesions that they termed "sebaceoma" consisted mainly of nests of basophilic cells with
some cystic structures, but mostly monomorphous basophilic cells studded with sebocytes. These lesions
were very different from the sebaceous adenomas in the literature up to that point, those being more like
mature sebaceous glands but with a periphery of immature sebaceous glands eventually becoming mature in
pyramidal structures. The sebaceoma, however, had the structural pattern much like a cylindroma or
spiradenoma, but without the prominent basement membrane components with "jigsaw puzzle"-like patterns in
cylindroma, or the ducts and two-cell pattern of spiradenoma. In recent years a lesion that has been
termed "rippled pattern trichoblastoma" has been described. Ohata and Ackerman, in 2001, argued that
these so-called rippled pattern trichoblastomas were nothing more than sebaceomas because they were all
studded with sebocytes. (Dermatopathol Pract and Concept 2001; 7:355).
In the time between Troy's and Ackerman's description of what they termed "sebaceoma", and the
present, other authors such as Sánchez Yus and colleagues attempted to unify the idea of sebaceous
adenoma under the term "sebomatricoma". It became clear from looking at their figures that were
published in the Am J Dermatol 1995 (17:213) that this conglomeration of neoplasms included outright
sebaceous adenocarcinomas as well as some sebaceous gland neoplasms that were well differentiated and
very similar to those described by Rulon and Helwig as sebaceous adenoma. Some of the lesions they
described were very much like Troy's and Ackerman's lesions, and it becomes clear from looking at these
lesions that they were a conglomeration of different kinds of sebaceous gland neoplasms.
Thus, from the arguments and examples historic, beginning as sebaceous "adenomas" with abundant
sebocytic differentiation, to sebaceous adenocarcinomas, which were pleomorphic malignancies, it became
clear that abundant confusion had persisted in the literature about which lesions were malignant and
which ones were benign.
In 1998, Nussen and Ackerman challenged the concept of sebaceous adenoma one again by introducing the
idea that the classical sebaceous adenomas in the literature were nothing more than well differentiated
adenocarcinomas of sebaceous glands (Dermatopathol Pract Concept 4: 5-14). In that article, they
recounted previously published examples of lesions that were thought to be sebaceous adenomas. Their
take on this was that these lesions had enough nuclear pleomorphism and enough structural abnormalities
to be considered outright adenocarcinomas, and they included in this mixture of cases ones that they had
originally described as sebaceomas, so they themselves admitted that even they had the same problem of
prior authors. They went as far to say that, "We have changed our opinions about sebaceous adenomas and
cystic sebaceous adenoma not because of metastases but because of histopathological findings."
What were these findings? They believed that 1) the carcinomas contained confluence of aggregations
of neoplastic cells in an anastomotic patterns, 2) crowding of immature sebocytes, 3) slight pleomorphism
of immature sebocytes, 4) heterochromia of nuclei of immature sebocytes, 5) many sebocytes, especially
immature and even some mature ones in mitoses, 6) some mitotic figures were abnormal, 7) many individual
sebocytes were necrotic, indicated by pyknosis and karyorrhexis, 8) incipient necrosis en mass in some cases. All of these criteria were recounted in their article in
Writing in 2001, Mones and Ackerman, in the book, Resolving quandaries in
dermatology, pathology, and dermatopathology, cited that the reason for the confusion of sebaceous
adenoma and sebaceous carcinoma over the years was that the low-grade adenocarcinomas had been mistakenly
interpreted as adenomas. They believed that the concept of carcinoma should be expanded greatly and that
the true adenomas were actually a very small group of sebaceous gland neoplasms.
Thus, from 1998 to the present, there has been somewhat of a "buzz" in the community of those who
follow adnexal neoplasms because the way that sebaceous gland neoplasms have been studied historically in
light of the different interpretation by Ackerman, et al.
I believe that Nussen's and Ackerman's hypothesis of 1998 must be tested with real patients over a
period of time, and the hypothesis they have put forward needs to be taken seriously. At present, my
approach to these lesions is to state in reports that there is some controversy about the nature of many
sebaceous gland neoplasms. I tend to be more aggressive today in recommending excision of sebaceous
gland neoplasms, as I have expanded my own spectrum to consider more of them to be adenocarcinomas.
My bottom line is that one should think of sebaceous gland neoplasms today more seriously with
carcinoma in mind rather than writing them off as mostly adenomas.