It matched or surpassed the death toll from the bombing of the Church of Two Saints in Alexandria in January 2011, the previous worst church bombing. The attack came during Sunday Mass; the explosion occurred on the women's side of the church, so many of the dead were women and children, and the bombing came on the eve of Mawlid al-Nabi, the Prophet's birthday. Most of these details were widely reported.
But a particularly political connection of the site of the bombing has largely been missed. In fact, many of the reports have spoken of the location as taking place in a "chapel" of the Cathedral, or in a Church "attached" to the Cathedral.
The Church of St. Peter and St. Paul, known as the Butrusiyya, sits in the shadow of the Patriarchal Cathedral of Saint Mark, but it is a separate building that predates the Cathedral by several decades. The Butrusiyya was built in 1911, while the Cathedral was completed in 1968. The area around the cathedral is the site of numerous churches, some, like Anba Ruis nearby, dating from the 1400s. The land was given to the Church in Fatimid times.
The Butrusyya Church contains the grave of the original Prime Minister Boutros Ghali. So there are whole layers of potential political and sectarian symbolism.
In the photo below, the church of St. Peter and St. Paul is the Romanesque-style church in the center; the large Coptic-style vaulted church on the right is the Patriarchal Cathedral of St. Mark.