Unexpected presentation of accessory breast cancer presenting as a subcutaneous mass at costal ridge: a case report

Abstract

Background: During embryogenesis, bilateral thickening of ectoderm from anterior axillary folds to inguinal folds, called mammary ridges or milk lines, develops into breast tissues. Only a pair in the pectoral area is spared from regression and continuously develops into normal breasts. Accessory breasts can result if the regression process is incomplete. These ectopic breasts can change physiologically and pathologically similar to normal breasts. Unsurprisingly, they are capable of turning malignant. Reported cases show the most common area for accessory breast cancer to be the axillary area. We report a rare case of accessory breast cancer over the costal ridge. Case presentation: We present the case of a 51-year-old Asian woman who complained of an enlarged mass lower to her left breast developed over the period of 3 months while on contraceptive pills. Unaware that the mass could be an accessory breast, the primary doctor had prescribed oral contraceptives. After our patient had noticed that the mass was obviously growing, she decided to consult a surgeon as the mass continued to grow. Expected to be benign, the mass was investigated by ultrasonography and then excised surgically. A pathology report identified the mass to be a carcinoma of the ectopic breast tissue. However, sentinel lymph node biopsy showed no nodal metastasis of all four lymph nodes. Following surgery, she received chemotherapy, radiation, and antihormonal treatment. After 2 years of postoperative follow up, she remained free of disease. Conclusions: This patient was diagnosed as having accessory breast cancer which presented with a subcutaneous mass. As this condition is exceptionally rare but curable by early treatments, we recommend surgeons to consider potential malignancy when patients present with a subcutaneous mass.

Accessory breast cancer in the inframammary region: a case report and review of the literature

“…The classical Sappey's line serves as a "watershed, " defined as an imaginary line transversely connecting the umbilicus to the L2 on the back, separating the area of lymphatic drainage of the torso. The lymphatic drainage of the skin and subcutaneous tissue above Sappey's line is believed to drain into the ipsilateral axillary nodes, whereas that below the line drains into the ipsilateral groin nodes [3,17,18]. As in our case, the ipsilateral axillary nodes were sentinel nodes in five of six previously reported cases of ABC in IMR.…”

“…Although a few cases of ABC have been reported, most of them were located in the axillary region [ 1 , 2 ]. Our case is of great interest for several reasons: (1) ABC in the IMR is extremely rare [ 1 , 3 ]; (2) complete ABT consisting of the nipple, areola, and glandular tissue corresponding to Kajava’s Class I had been previously recognized because of congenital appearance and nipple discharge; (3) pathological diagnosis of the invasive ductal carcinoma and clinical staging of cT1N0M0: Stage IA were properly performed before surgery; and (4) sentinel nodes could be detected and confirmed to be free from involvement by a RI/ICG-fluorescence double method so that nodal staging was assessed and clearance could be avoided.…”

“…The incidence of ectopic breast cancer, including the aberrant type, is low, i.e., 0.2–0.6% of all breast cancers. The most common location is the axilla (60–70%), although it can develop in other less common locations such as IMR (5–10%) and rarely in the thighs, perineum, groin, and vulva [ 3 , 13 , 15 ]. Of the 1,148 cases of primary breast cancer we encountered from 1992 to 2020, only five (0.44%) were ABC, and all four previous cases were in the axilla.…”

“…We found six case reports of ABC in the inframammary or upper abdominal region [ 1 , 3 , 6 , 16 – 18 ]. Madej et al reported a case of advanced cancer (pT4N1M0: stage IIIB) [ 16 , 19 ].…”

“…Therefore, nodal metastasis had to be considered, and SNB was performed 7 days after excision. This case had an early stage (pT1cN0M0: stage IA), similar to our case [ 3 , 19 ].…”