Introduction:

Metastatic deposits to the breast from extramammary malignancies are rare and account for only 0.3% to 2.7% of all malignant breast tumors [1,2]. Clinically and radiologically, metastatic malignancies from extramammary sites may masquerade neoplasms of the breast, sometimes even benign ones [1]. A correct diagnosis of metastasis to the breast is of paramount importance as the treatment of primary and secondary malignancies of the breast is different.

We have reviewed 4 cases of metastatic neoplasms to the breast which were diagnosed in the 5-year period. Metastases from primary breast carcinoma were excluded.

Case Reports

Case 1:

A 67-year-old postmenopausal lady was on chemotherapy and regular follow-up as biopsy from her neck nodes revealed metastatic deposits of unknown origin. 19 months later, she came with complaints of abdominal pain. On examination, she was found to have ascites. USG abdomen revealed moderate ascites with right ovarian cyst and septations. Omental nodule was also seen. The ascitic fluid was aspirated and USG-guided FNAC of the omental nodule was done. Both the samples revealed pleomorphic cells arranged in clusters and papillaroid patterns with signet ring cells (Figure 1a). Immunohistochemical analysis on the cell block, showed tumor cells positive for CK7 and WT1 (Figure 1b). She was diagnosed with metastatic adenocarcinomatous deposits from ovary. 10 months later, the patient came with lump in both breasts. She had noticed the lump first in the right breast and then in the left. USG-guided trucut biopsy was performed and it revealed malignant cells with the same morphology as that described in the omental nodule. Immunohistochemistry was done and the neoplastic cells expressed strong positivity with WT1 and PAX8. They were negative for GCDFP-15 (Figure 1c), thus ruling out a primary breast carcinoma.

Fig.1 - Ovarian serous papillary adenocarcinoma

Case 2:

A 43-year-old lady, presented with lump in the left breast. Clinically and radiologically, it was diagnosed as carcinoma breast. USG-guided trucut biopsy was done and it showed monotonous population of small round blue cells arranged in diffuse sheets (Figure 2). After further immunohistochemical markers study, it was diagnosed as mantle cell lymphoma. On further detailing, it was revealed that 6 months earlier, patient had generalised lymphadenopathy and biopsy of the cervical lymph node was done. On retrieving the cervical lymph node biopsy sections, it showed monotonous population of small round cells with the same morphology as that seen in breast, and the immunohistochemistry confirmed it to be non Hodgkin lymphoma (Mantle cell type). The breast diagnosis was given as metastatic lymphoma. She is currently on chemotherapy.

Fig.2 – NHL - Mantle cell lymphoma

Case 3:

A 37-year-old lady presented with complaints of abdominal distension, pain abdomen and decreased urine output. On physical examination, there was ascites and bilateral hard breast lumps. The patient attributed the hard lumps in the breasts to her sudden weaning from breastfeeding her 1 and half year baby, due to her general weakness. Her CT abdomen revealed pancreatitis, superior mesenteric vein thrombosis and a pancreatic lesion with lytic lesions in the pelvic bone. Findings were initially suggestive of primary lesion in the pancreas or bilateral breasts which would have given rise to several bony secondaries. Ascitic fluid analysis showed florid mesothelial cell hyperplasia with scattered atypical cells. Trucut biopsy from the breast revealed a poorly differentiated neoplasm (Figure 3a) which was diagnosed as plasmacytoma after IHC studies (Figure 3b). Her creatinine was elevated and she had to be put on dialysis. Serum protein electrophoresis done on the consecutive days, revealed monoclonal spike in the gamma region. Bone marrow aspiration and biopsy were done and it was diagnosed as plasma cell dyscrasia (Figure 3c). Surgery for the breast lumps was diverted and patient was started on chemotherapy for Multiple Myeloma.

Fig.3 - Plasmacytoma

Case 4:

A 54-year-old postmenopausal lady presented with complaints of swelling in the right inguinal region since 4 months and lump in the left breast since 2 months. She gave past history of foot ulcer excision which was diagnosed as malignant melanoma, 2 years ago. USG-guided trucut biopsy of the breast lump was done at another center and was reported as invasive ductal carcinoma. At our center, PET scan was done which showed uptakes in the right inguinal region and breast with no uptake elsewhere. Based on the reports, a provisional diagnosis of double malignancy (left breast carcinoma and right inguinal malignant melanoma) was made. She underwent left modified radical mastectomy and right ileo-inguinal block dissection. The biopsy sections of the mastectomy specimen and inguinal nodes revealed same morphology of sheets of pleomorphic cells arranged in sheets with intracytoplasmic and extracellular pigment deposition (Figure 4a). The diagnosis on the mastectomy specimen was given as metastatic malignant melanoma after IHC studies (Figure 4b). She is currently on chemotherapy.

Fig.4 – Malignant melanoma

Hence from the above discussed cases, 2 cases presented with breast lump during presentation, of which 1 was misdiagnosed as primary breast carcinoma. Had it been diagnosed as secondaries in breast, treatment would have been restricted to palliative chemotherapy and a modified radical mastectomy could have been avoided. This highlights the significance of relevant clinical history, correct histopathological diagnosis and the challenge behind differentiating secondaries in breast from primary breast disease.

Discussion

Secondaries to the breast are rare. In large studies they have been reported to constitute 0.3–2.7% of all breast malignancies [1-3]. The most common are lymphomas, tumors of hematopoietic origin, followed by ovarian adenocarcinoma, malignant melanoma and bronchogenic carcinomas [4,5]. Clinically, a breast metastasis usually presents as a rapidly growing, single, firm mass that is usually mobile, not tender and located more often in the left breast and the upper outer quadrant. Both breasts can be involved. Typically, tumours appear discretely in the breast displacing normal breast tissue rather than arising from them [6]. By imaging, many different appearances of metastatic tumors in the breast can be seen. They may masquerade as a probably benign lesion or could be similar to primary breast carcinomas [7, 8]. Lee et al reported that only 2 cases in their series of 33 cases, were classified as BIRADS 3, the rest being categorized as BIRADS 4b or higher [8].

The majority of patients who present clinically with metastatic breast tumour have a known primary elsewhere. However, a small subset of patients present with occult primary disease and breast metastases are the first manifestation of the disease. Metastatic melanoma is a mimicker of a broad spectrum of primary breast lesions. Due to the varied morphological patterns, including epithelioid, spindle and plasmacytoid cells, there could be overlap with mammary carcinoma. Awareness of this is essential to avoid inappropriate treatment, especially in ‘‘triple negative,’’ poorly differentiated carcinomas of the breast. Although the application of a simple panel of antibodies assists in correct interpretation, lesions presenting as isolated breast tumors may introduce a significant diagnostic difficulty, especially when there is inadequate patient history and limited biopsy material. A long interval between primary diagnosis or the first appearance of malignancy and breast metastases could also result in misdiagnosis of the tumour for an infiltrating primary carcinoma of breast. Therefore, along with biopsy sections, a good clinical history and application of immunohistochemical stains is mandatory.

Treatment of breast metastases should be directed at the primary disease. Surgical therapy is widely recommended to be mostly conservative whenever possible and commonly entails wide local excision. Treatment for isolated metastatic disease may be palliated by surgical resection with few cases having good prognosis. In the majority of cases the prognosis is poor. Large bulky tumours may be palliated by mastectomy though this procedure should be avoided whenever possible. In specific tumours such as carcinoid, lymphomas and choriocarcinomas, chemotherapy is found to give symptomatic relief with prolonged survival in select patients. Survival in patients with metastatic lymphoma is related to stage and histologic characteristics. Patients with higher grade histologic lesions or more advanced stage have a worse prognosis. Advanced melanoma, though usually refractory to systemic therapy, may occasionally respond to treatment with biologic response modifiers and cytotoxic agents.

Conclusion

Metastases to the breast needs to be considered if the histological appearance is unusual for a primary mammary tumour. In some cases the histological appearance is similar to a primary mammary tumour and hence the clinical history with relevant investigations are essential to making the accurate diagnosis and definite management.

References

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