33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

Case 1:
History: 65 y/o female with 2.5 cm ill-defined left breast mass with firm, tan cut
surfaces.
Submitted diagnosis: Invasive lobular carcinoma.
INVASIVE LOBULAR CARCINOMA
Background: The classical type of invasive lobular carcinoma is a well-recognized
invasive breast lesion (1-9); but, other forms of this tumor, including pleomorphic,
solid, alveolar, mixed, apocrine, signet-ring, tubulolobular, and histiocytoid
(“myoblast-omatoid” or “granular-cell”) variants are less well known (1-20). Some
studies have focused on the clinicopathologic significance of these infiltrating lobular
carcinoma variants and have shown that solid, alveolar, mixed, and signet-ring forms
apparently have a poorer prognosis than the classical variant (6-15 and 57). Fisher et
al. (1) reported that the short-term treatment failure rates in patients with tubulolobular
invasive carcinoma were intermediate between those of tubular carcinoma and
infiltrating lobular carcinoma, suggesting that this variant had a better overall
prognosis than some others. Similar findings were reported by Ellis et al. (2) who
found that the classical, tubulolobular, and lobular mixed types were associated with a
better prognosis than ductal carcinomas (no special type [NST]), but this was not true
for the solid variant of infiltrating lobular carcinoma, which showed a prognosis
similar to ductal NST. Too few cases of the histiocytoid and/or apocrine variants of
infiltrating lobular carcinoma have been reported to make firm conclusions as to their
behavior relative to other variants of infiltrating lobular carcinoma (11,12); however,
recent work suggests that the apocrine variant displays aggressive behavior (16). It is
important to know about these variants to avoid under diagnosing them as benign
lesions such as reactive benign histiocytes, fibrohistiocytic lesions, or granular-cell
tumors. Keratin immunostaining of carcinoma cells can be used to avoid this pitfall.
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