Primary signet-ring cell carcinoma of lung

Signet ring cell carcinoma may arise in the stomach, colon, breast, bladder or prostate. It is a rare primary pulmonary tumour: most cases of signet-ring cell carcinoma in the lung are metastatic.

Histopathology

A large mucin droplet displaces the nucleus to the edge of the cell. To be classified as a signet-ring cell carcinoma, more than 30% of the tumour should show a signet-ring cell morphology. The signet ring cells may show a diffuse architecture or may form acinar structures. There are no reliable morphological features differentiating primary from metastatic signet ring cell carcinoma of the lung.

Immunohistochemistry with signet ring cell carcinomas of stomach, colon and breast for comparison:

	lung	stomach	colon	breast
TTF-1	14/171, 2/22, 1/13, 6/64	0/51	0/51	0/51
villin	5/171	5/51	5/51	1/51
CDX-2	0/22	variably positive	positive
MUC2	0/22	variable	positive
MUC5AC	1/22	positive	variable
SP-A	1/22	negative	negative
CEA	9/94
GCDFP-15	0/64
ER	0/64
PR	0/64
CK7+/CK20+	1/171	2/51	0/51	0/51
CK7+/CK20-	16/171, 2/22, 3/64	2/51	0/51	5/51
CK7-/CK20-	3/64	0/51	0/51	0/51
CK7-/CK20+	0/171	1/51	5/51	0/51

Immunoreactivity of mucinous carcinoma of lung other than signet ring cell type is on another page.

Differential diagnosis

• Metastatic signet ring cell carcinoma.

• Mucinous (so-called colloid) carcinomas of the lung: distinguished from signet ring cell adenocarcinoma of the lung by the presence of extensive pools of mucin; the neoplastic tumour cells floating in the mucin most often display the features of conventional mucin-secreting adenocarcinoma cells and only rarely may show focal signet ring cell features. Mucinous carcinomas that are amenable to complete surgical resection usually follow a much more favorable prognosis than signet ring cell adenocarcinomas.

• Acinic cell carcinoma of the lung may show a prominent alveolar or acinar growth pattern and the tumour cells can occasionally resemble signet ring cells creating a similarity to signet ring cell carcinomas of the lung. In these cases, histochemical stains for mucin will be of great importance. Unlike signet ring cell carcinomas, the cells in acinic cell carcinoma are generally negative for mucicarmine. Acinic cell carcinomas are tumours of low-grade malignancy that respond well to complete surgical resection.

• Mucoepidermoid carcinoma: may contain mucocytes in which the intracytoplasmic mucin has displaced the nuclei towards the periphery of the cells. The presence of an epidermoid cell component admixed with the mucocytes and the bland cytological features of the mucinous cells in general will be of help in arriving at the correct diagnosis. Low grade mucoepidermoid carcinomas have a very favourable prognosis and complete surgical resection is the treatment of choice.

Prognosis

This is an aggressive tumour^2,4.

References

¹Merchant, S. H., Amin, M. B., Tamboli, P., Ro, J., Ordonez, N. G., Ayala, A. G., Czerniak, B. A., Ro, J. Y. Primary signet-ring cell carcinoma of lung: immunohistochemical study and comparison with non-pulmonary signet-ring cell carcinomas. Am J Surg Pathol 2001;25:1515-1519

²Rossi, G., B. Murer, et al. (2004). "Primary mucinous (so-called colloid) carcinomas of the lung: a clinicopathologic and immunohistochemical study with special reference to CDX-2 homeobox gene and MUC2 expression." Am J Surg Pathol 28(4): 442-52.

³Stenhouse, G., N. Fyfe, et al. (2004). "Thyroid transcription factor 1 in pulmonary adenocarcinoma." J Clin Pathol 57(4): 383-7.

⁴Castro, C. Y., C. A. Moran, et al. (2001). "Primary signet ring cell adenocarcinomas of the lung: a clinicopathological study of 15 cases." Histopathology 39(4): 397-401.

This page last revised 1.10.2004.

©SMUHT/PW Bishop