26-year-old female with no significant comorbidities.

The patient initially presented with anal pain, mild rectal bleeding, and episodes of constipation lasting four months. She consulted a gastroenterologist, who performed a colonoscopy and biopsy, revealing a rectal tumor. She was subsequently referred to the University Hospital for further evaluation and management.

-General Examination: WHO performance status 0; conjunctiva normally colored.

-Abdominal Examination: Soft abdomen, normal breathing, no signs of tumor syndrome (e.g., no hepatomegaly or splenomegaly).

-Anal Margin Examination: No fissures or fistulas.

-Digital Rectal Examination: Presence of an exophytic process 5 cm from the anal margin; good sphincter tone.

-Lymph Nodes: No palpable inguinal or supraclavicular lymphadenopathy.

-Liver function tests and complete blood count were within normal limits.

-Serology for hepatitis B, hepatitis C, and human immunodeficiency virus were negative.

-Serum carcinoembryonic antigen (CEA) levels were mildly elevated.

An ulcerative, exophytic lesion located 8 cm from the anal margin on the left lateral wall of the rectum, extending over 5 cm. The mucosa beyond this point appeared macroscopically normal.

Conclusion: Ulcerative-exophytic rectal lesion.

Rectal biopsy revealed a poorly differentiated and infiltrating Lieberkühnian adenocarcinoma.

Thoraco-abdominal-pelvic CT Scan:

-Tumor involving all three segments of the rectum with extramural extension > 5 mm and a circumferential resection margin (CRM) < 1 mm.

-Mesorectal and left internal iliac lymphadenopathy.

-No distant metastases.

-Classification: T3 N2 M0.

-The patient underwent ovarian transposition before starting radiotherapy.

-Initial treatment included concurrent radiochemotherapy using the Cap50 protocol (The Cap50 protocol, consisting of capecitabine-based chemoradiotherapy, was chosen due to the locally advanced stage of the tumor (T3N2), aiming for tumor downstaging and potential organ preservation), followed by two cycles of Folfox (organ preservation protocol), then the patient was lost to follow-up for two months due to personal reasons.

Upon returning, the patient reported the appearance of bilateral breast nodules shortly after completing the two cycles of Folfox.

Mammography and Ultrasound:

Immunohistochemical Analysis:

Physical Examination:

Further Investigations:

Multidisciplinary Consultation Meeting (RCP):

Emergency Surgery and outcome:

Most metastases appear as palpable breast masses, sometimes adhering to the skin, with a slight predominance on the left side, typically located in the upper outer quadrant. Multiple or bilateral lesions are rarely observed [3] . Schakelford et al. reported that 55% of breast metastases occurred on the left, 30% on the right, and only 3% involved bilateral breast metastasis. Toombs and Kalisher noted that pain, tenderness, or discharge are rarely observed, and nipple retraction has not been reported, although adherence to the skin has been reported in 25%. Axillary node involvement was frequently encountered. Rumana, Rakesh Kumar, Ruiz, et al. [5] [6] reported cases of bilateral breast metastasis in young patients exist. Suganthi Krishnamurthy documented the youngest patient, a 23-year-old, with rectal cancer metastasizing to the breast. Hisham et al. [1] described an unusual case of rectal carcinoma metastasizing to the breast, accompanied by ocular involvement. Mihai et al. reported a 53-year-old woman who developed breast metastasis followed by cutaneous metastasis after chemotherapy, exhibiting a disease progression [7] .

The time from the initial diagnosis to the development of breast metastasis ranges from 1 month to 15 years, with an average of 1 to 5 years. Hasukic et al. [8] reported a 69-year-old patient who developed breast metastasis 30 months after undergoing an abdominoperineal resection. Ting Wang et al. reported a 38-year-old male who, after undergoing an anterior resection,developed breast metastasis 7 years later. Differentiating between primary and metastatic breast neoplasms can be challenging. Mammograms are useful in resolving uncertainties. The typical mammographic finding is a rounded, well-circumscribed mass without speculation, microcalcifications,or skin thickening [3] .

The typical ultrasound (US) features of hematogenous metastases include single or multiple well-defined, round to oval-shaped, hypoechoic masses without spiculations, calcifications, or architectural distortion. These masses are typically located superficially in the subcutaneous tissue or directly adjacent to the breast parenchyma.

Histologically, metastatic tumors display the same morphological characteristics as the primary tumors. Excisional or incisional biopsy is the most frequently employed procedure for differential diagnosis [9] . There is a growing preference for needle core biopsy over fine needle aspiration cytology. In his study, Silverman reported 2529 FNA breast biopsies, of which 666 were malignant, with only 18 originating from extra-mammary malignancies. In a series of 10,650 breast biopsies from the Mexican population, Alvarado et al. reported 24 cases of extra-mammary malignancies. In most cases, immunohistochemistry is useful for making an accurate diagnosis. Testing for the expression of CK7 and CK20 is particularly helpful. The majority of primary breast cancers are CK7-positive and CK20-negative, whereas colorectal carcinomas are typically CK7-negative and CK20-positive. Mucinous differentiation in colorectal cancer is linked to a poor prognosis. In this case, the intense CDX2 expression confirmed the gastrointestinal origin of the breast nodules.

Most patients with secondary breast cancer succumb to the aggressive progression of the disease within a year of the primary tumor diagnosis. Surgical treatment is typically palliative, with mastectomy playing a limited role. Systemic chemotherapy is essential for these patients, and while metastasectomy combined with effective chemotherapy can extend survival, its primary role remains palliative [3] . Treatment options for patients with metastatic colorectal cancer (mCRC) have evolved significantly with the advent of anti-epidermal growth factor receptor (EGFR) therapies that target the EGFR signaling pathway. KRAS genotyping is essential before starting anti-EGFR monoclonal antibody therapy in mCRC patients, as KRAS mutations are a strong and reliable negative predictive factor for the effectiveness of anti-EGFR monoclonal antibody treatments.

This case is consistent with previous reports of rapid disease progression and poor outcomes in young patients with breast metastases from rectal cancer. The patient’s refusal of further treatment highlights the psychosocial challenges in managing advanced cancer.

Among the 13 cases summarized in Table 1 , the majority occurred in women aged 23 to 69, with a tendency toward unilateral presentation, particularly in the upper outer quadrant. The most frequently used diagnostic tools included ultrasound, CT, and core needle biopsy. Immunohistochemistry was consistently useful in confirming gastrointestinal origin through CDX2 positivity and absence of GATA3. Treatment strategies varied, but outcomes were generally poor, with a survival time post-breast metastasis ranging from 2 to 12 months [10] .