Rosen's Breast Pathology, 4e

907

Unusual Clinical Presentation of Carcinoma

are sometimes suggestive of metastatic malignant melanoma (Fig. 33.15), and metastatic renal cell carcinoma may be considered if cytoplasmic clearing is prominent. When the tumor cells are dispersed singly or in small groups through­ out a lymph node, the resulting pattern might be confused with diffuse malignant lymphoma (Fig. 33.16). Small well- differentiated glandular metastases in an otherwise hyper­ plastic lymph node may be the presenting manifestation of an occult tubular carcinoma (Fig. 33.17). In these cases, the lymph node is enlarged by lymphoid hyperplasia, possibly in response to the metastatic carcinoma. Metastatic tubular carcinoma should not be misinterpreted as benign glandular inclusions (see Chapter 43). About 20% of ALN metastases consist of adenocarcinoma with growth patterns similar to those more commonly en­ countered in primary carcinomas in the breast. These include cribriform, papillary forms of invasive carcinoma (Fig. 33.18). A desmoplastic stromal reaction is rarely present in these nodal metastases. The remaining 15% of the lymph nodes contain mixtures of tumor with the conventional patterns and diffuse apocrine cells. Metastatic carcinoma from a nonmam­ mary site such as the lung may be difficult to distinguish from these mixed types of breast carcinoma (Fig. 33.19). Approximately 50% of the lymph nodes involved by each of the three patterns of metastases have some mucicarmine- positive cells. Among cases in which tissue blocks were avail­ able to cut fresh sections for the mucicarmine stain, 75% gave a positive reaction. A positive result with this simple procedure narrows the differential diagnosis substantially, especially when gland formation is not apparent. It is not unusual to find mucin-positive cells limited to isolated tu­ mor cells in only one of several involved lymph nodes. If a diagnosis of adenocarcinoma is not apparent from the growth pattern and mucin stain, other studies may be helpful. Immunohistochemical studies for cytokeratins, especially CK7 and CK20, hormone receptors, epithelial

Ta b l e 3 3 . 1  Lymph Node Pathology in Patients With and Without Primary Breast Carcinoma With Primary Without Primary

(N = 31) No. (%) 20 (65)

(N = 12) No. (%)

Large apocrine cells Mammary carcinoma pattern

8 (67)

7 (23)

1 (8)

Mixed pattern 3 (25) Adapted from Haupt HM, Rosen PP, Kinne DW. Breast carcinoma presenting with axillary lymph node metastases. An analysis of spe- cific histopathologic features. Am J Surg Pathol 1985;9:165–175. 4 (13)

Microscopic Pathology of ALNs Metastatic adenocarcinoma found in the ALNs derived from an occult breast carcinoma usually has one of three patterns found in ductal carcinomas (Table 33.1). In about 65% of cases, the lymph nodes contain extensive infiltrates of large cells, often with apocrine features, diffusely distributed in the lymphoid tissue as well as in sinusoids (Figs. 33.12 and 33.13). Less often, the lymph nodes contain predominantly sinusoidal metastases. Apocrine features include substantial cytoplasmic eosinophilia in most instances, but in some me­ tastases there is prominent cytoplasmic clearing (Fig. 33.14). Little or no gland formation is evident in these metastases, but mucicarmine-positive secretion can be demonstrated in at least a few cells in most cases. Nuclei tend to be large, round or oval, and to be vacuolated with prominent, fre­ quently eosinophilic nucleoli. This cell type and distribution

FIG. 33.12.  Occult carcinoma. A: Metastatic adenocarcinoma in an ALN. The tumor cells have apo- crine features consisting of abundant, finely granular eosinophilic cytoplasm, large open nuclei, and prominent nucleoli. B: This microscopic focus of intraductal carcinoma with periductal fibrosis and lymphocytic reaction was the only parenchymal lesion in the mastectomy specimen.